A slippery slope is a fallacy that assumes a small action will lead to a chain of events. If we allow A, then B will happen, then C, then D, and eventually disaster. The chain is not proven. The connections are assumed. The slope is slippery. The first step leads to a fall.

The fallacy is common in politics and parenting. If we allow same-sex marriage, then people will marry animals. If we let children stay up late, they will fail school. The chain is exaggerated. The connections are weak. The conclusion is fear-mongering. The slippery slope avoids evidence. It relies on emotion.

Slippery slope examples

• If we ban assault rifles, soon they will ban all guns.
• If you give a mouse a cookie, he will want a glass of milk.
• If we allow euthanasia, we will start killing the disabled.
• If you smoke one cigarette, you will become a chain smoker.
• If we legalize marijuana, we will legalize heroin next.

The slippery slope is not always fallacious. Sometimes small actions do lead to big consequences. The domino theory in the Vietnam War was a slippery slope argument. It was debated. The question is whether the chain is probable. Is there evidence for each link? Is the slope actually slippery? The fallacy occurs when the chain is asserted without evidence. The remedy is to ask: what is the evidence for each step? Is the chain inevitable? Usually it is not. The slippery slope is a warning. Sometimes the warning is valid. Sometimes it is a scare tactic. The difference is evidence. Without evidence, the slope is just a slide into fear.